Doug Johnson, Extension Entomologist, University of Kentucky
I have received reports that appear to indicate an increase
in brown marmorated stink bug (BMSB) activity in central Kentucky. This
invasive bug which has a wide host range has been in Kentucky for about five
years, but as yet has not become of economic importance in grain crops. This is
likely to change at some time, and it is best to not get caught unawares!
Fig. 1. Known distribution of BMSB in KY. |
At
present this pest is likely to be more important to soybeans and possibly corn grown
in central and eastern KY (Figure 1.) as
opposed to those grown in western KY. You can keep abreast of the known
distribution of this insect by checking with UK Extension Entomology at: http://pest.ca.uky.edu/EXT/BMSB/welcome.html.
BMSB is mainly a
threat because of it’s’ ability to develop very large populations. Bug to bug
it is not a great deal more important than other brown or green stink bugs, but
its’ populations tend to be much larger. Like other stink bugs BMSB begin
moving into soybeans as they start to bloom and populations grow to their
largest numbers as pods are forming and filling. It is their feeding on pod that’s
important.
Sampling for stinkbugs in soybeans is rather straight forward
and best done with a 15” sweep net. Sample several locations across the field
taking 25 sweeps at each location. Count the number of stink bugs in each (25 sweep)
sample and average them over the field. The treatment threshold for stink bugs
during flowering and podfill (R1-R6) is an average of 9/25 sweeps. BMSB tend to be highly congregated on the field margins.
Though some will be found in the interior of a field, most of them will be in
the outer rows. In many states edge applications have been found to be
sufficient to control this pest.
Fig. 2. BMSB diagnostic characters. |
BMSBs look similar to
other brown stink bugs in shape and color, though they tend to be a bit larger.
The most diagnostic characters for identification are the two (small but
distinct) white strips on each antenna near the tip end. Also, along the rear
sides are a series of black and white bands (Figure 2.). These insects can be controlled reasonably well with
synthetic pyrethyroid insecticides. In particularly difficult situations,
mixtures of pyrethroids + neonics or pyrethroids + acephate may provide a
little better control. You can find insecticides for use on stink bugs in
soybeans in ENT-13 which may be found on the web at:
or from your County Extension Office.
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